Western Port and Catchment

The Port Phillip Bay, Western Port and Gippsland Lakes Report Card was developed to report on the water quality at sites in Port Phillip Bay, Western Port, the Gippsland Lakes and their surrounding catchments. Click on the map or list below to explore.

Included on the map are the locations of water quality monitoring sites used in the calculation of the catchment Water Quality Index (WQI) scores.

Western Port and Catchment

Report Card for July 2016 – June 2017

This is the first Water Quality Report Card for Western Port and its associated catchment. It provides a snapshot of water quality from 1 July 2016 to 30 June 2017. The quality of the water is given an overall score by combining the results of a number of standard water quality parameters: nutrients, water clarity, dissolved oxygen, salinity, pH, metals and algae.

In 2016–2017, water quality in Western Port was ‘Very Good’ and its catchment’s water quality was ‘Poor’.

Summary Table: The table below shows the percentage of Western Port and surrounding catchment that fall into each scoring category. See the scoring method for more information.

Area

Score

18.4%

Very Good
Near-natural high quality waterways

Western arm of Western Port

2.9%

Good
Meets Victorian water quality standards

Tributaries in the upper catchment

40.4%

Fair
Some evidence of stress

Eastern arm of Western Port and the Bunyip and Lang Lang Rivers in the mid and upper northern catchment

22.6%

Poor
Under considerable stress

Small creeks in the North, on the Mornington Peninsula and the mid Bass catchment

15.7%

Very Poor
Under severe stress

Watsons Creek, Wylies Drain in the north and the lower Bass River

In 2016–2017, routine monitoring occurred across 35 sites in catchments of Western Port, with 2 of these sites located within the bay itself. This represents 61 per cent of the total catchment area. The remaining 39 per cent of the catchments, which are not monitored, are mostly rural and would typically score as ‘Poor’.

The section Changes over time compares the 2016–2017 Report Card scores and indicators for Western Port and catchment to previous annual Water Quality Index (WQI) scores generated since 2000. More detail on Western Port and its catchment is provided in their individual reports.

Site-specific details within Western Port and its catchment can also be accessed directly from the map or within the individual catchment and Western Port reports.

How did the climate impact on water quality?

Annual and seasonal variability in rainfall, temperature and solar exposure (how sunny it is) can impact on water quality in Western Port and catchment waterways.

Rainfall mostly impacts on water quality in waterways. High rainfall events can increase the amount of runoff, carrying sediments, nutrients and pollution into waterways, which reduces water quality. Low rainfall can result in low dissolved oxygen levels and increased salinity, which also results in reduced water quality. In 2016–2017, rainfall across the region was near average in the northern catchments of Western Port and slightly below average in the eastern catchment.

While annual rainfall was near average, monthly rainfalls exceeded long term averages in October 2016, from January to April 2017 and in June 2017. Regular high-rainfall events (greater than 20 millimetres) also occurred across the catchment, resulting in slight declines in water quality in tributaries in the northern catchment of Western Port, as was observed in the Cardinia Creek at Upper Beaconsfield site. This was associated with runoff to tributaries in rural and natural areas of the upper catchment. These small waterways tended to show higher levels of sediment and nutrients because the effects of runoff are more concentrated over a small area.

In Western Port, water quality can be impacted by waterway discharges from the surrounding catchment, particularly in areas close to river mouths and discharge points. Waterway discharges were close to average for the Lang Lang and Bass rivers while the Bunyip River was above average. Low stream-discharge into Western Port reduces the input of sediments, nutrients and pollutants. However, reduced discharge can lead to increased salinity, particularly in summer.

During summer, when temperatures are warmer and solar exposure is high, salinity in the shallow north-eastern mudflats region can exceed the normal oceanic range as a result of evaporation. In 2016-2017, summer temperatures were close to average and solar exposure was slightly below average; combining these climatic variables with above average rainfall in the catchment over summer counteracted the effects of evaporation, maintaining salinity levels within the normal oceanic range.

Events

The Report Card's water quality index is based on routine sampling which means the short-lived environmental and weather events that can impact water quality are not always captured. The following events occurred during the 2016–2017 reporting period:

On 29 December 2016 and 10 April 2017, storms brought heavy rain to the northern catchment. Other high rainfalls (greater than 20mm) occurred in July and October 2016, and in January, February, March, April and June 2017. During April, several high rainfall events resulted in decreased water clarity and increased nutrient levels in the upper catchment. This was evident in the Upper Tarago River, the Bunyip River in the lower catchment and Corinella within Western Port.

Environmental flow releases (controlled releases of water) occurred in the lower Tarago River. Three environmental flows, with a total of 1,952 million litres of water, were released into the lower Tarago River to maintain water quality, to provide habitat for River Blackfish, platypus and macroinvertebrates, and to support spawning of Australian Grayling.

Merricks Creek Estuary Mouth. Source: Geoff Hall, EstuaryWatch

Sea Search volunteer with a Pencil Urchin in the French Island Marine National Park. Source: Marks Rodrigue, Parks Victoria

Changes over time

Since 2000, water quality in Western Port has generally been ‘Good’ to ‘Very Good’ and water quality for the catchment has consistently been ‘Poor’.

During times of low rainfall, the water quality of some streams may improve as there is little to no input from runoff. This results in lower levels of nutrients and pollutants, and improved water clarity. However, low rainfall for some streams can reduce flows to the point where dissolved oxygen declines to levels that impact the aquatic life. Low stream-discharge into Western Port can also reduce the input of nutrients and pollutants. However, reduced freshwater inflows can lead to increased salinity above the normal oceanic range, particularly during summer when evaporation rates can exceed catchment inflows.

During times of high rainfall, the catchment streams are impacted by increased runoff, which decreases water clarity and increases levels of nutrients and pollutants that enter waterways. This results in high stream-discharges being delivered into Western Port, which increases levels of catchment derived sediments and pollutants in the bay and potentially encourages algal growth due to increased nutrient availability. At these times, low water clarity decreases the availability of sunlight, necessary for photosynthesis, and limits algal growth. Algal blooms are not common in Western Port due to the strong tidal exchange with Bass Strait. Large freshwater inputs also lead to low levels of salinity, below the normal oceanic range, as occurred during winter and spring from 2010-2014.

Gradual water quality improvement in the catchment waterways have occurred since the drought-breaking rains arrived in 2010. The overall water quality in Western Port has fluctuated due to variable river discharge volumes altering salinity and algae levels. Sediment and nutrient inputs to Western Port are also dependant on discharge volume. Additional to catchment derived sediment and nutrient inputs to Western Port, internal processes also contribute to decreased water clarity and increased nutrient levels, further reducing water quality; these include the erosion of the eastern mud cliffs by wind generated waves, and the resuspension of sediments and nutrients from tidal movement and wind generated waves in the north-eastern mudflats region.

Due to a small number of monitoring events in Western Port, no WQI scores were calculated from 2005-2008. See the Monitoring Programs page for more details about the monitoring program.

Plot of water quality index (WQI) score history for Western Port and its catchment.

Actions

What's happened?

The Government, authorities and community have implemented a number of initiatives to improve waterway health in Western Port and catchment, including these outlined below:

led the Western Port environment research program in partnership with other Victorian government agencies and scientific experts, to improve knowledge and health of Western Port marine and coastal environment.

Parks Victoria, as part of the ‘Healthy Parks Healthy People’ project, planted 500 mangroves along the foreshore in Western Port in an effort to reduce wave erosion of the cliffs along the foreshore abutting the Churchill Island Marine National Park.

The Western Port Ramsar Site Management Plan was finalised, led by the Department of Environment, Land Water and Planning (DELWP), with contributions from Melbourne Water, Port Phillip and Westernport Catchment Management Authority and Environment Protection Authority Victoria (EPA). Implementation is underway.

The Victorian Government has prioritised the protection and improvement of Victoria's water environments. To ensure Victoria has clear and relevant standards, legal rules and statutory obligations to protect and improve the health of our water environments, the Government is reviewing two key policies: State Environment Protection Policies (SEPPs) for Waters of Victoria and Groundwaters of Victoria. The review is expected to be completed in 2018.

Environment Protection Authority (EPA) introduced the $2 million 2014-2017 Litter Hotspots grants program in 2014. This program is led by the Melbourne Waste and Resource Recovery Group, working with local councils and community groups to find local litter solutions.

For more information about projects and works in the Western Port catchment in 2016–2017, please see the Waterways Local Updates.

What's planned?

A number of priority areas and actions have been identified for Western Port and catchment that will build on existing projects and initiatives. Priority management actions include:

Melbourne Water is implementing their ‘Healthy Waterways Strategy’ and ‘Stormwater Strategy’. These strategies cover the five years from 2013–2014 to 2017–2018 and contain information about planned actions to improve the health of rivers and creeks in the Western Port catchment. These strategies are also in the process of being refreshed, with community consultation underway.